Plastisol having polymer particles dispersed in a plasticizer as a medium is used in a wide range of industries, and its industrial value is remarkable. Plastisol using the most common vinyl chloride polymer is known as vinyl chloride sol, and it is used in a broad range of fields, such as vehicle undercoats, vehicle body sealers, carpet backing materials, wallpaper, floorings, paints, and disposable gloves, due to its excellent physical properties.
A variety of performances are required for plastisol, and one of them is low viscosity. When plastisol has low viscosity, the speed of passing through processes can be improved and the amount of an extender to be blended can be increased, resulting in lower production costs.
In recent years, it has been pointed out that vinyl chloride polymers commonly used in plastisol have possibility to generate harmful hydrogen chloride gas and dioxin depending upon a disposal and incineration method. As a material to overcome this problem, acrylsol having acrylic polymers dispersed in a plasticizer is proposed in Japanese Patent Laid-Open No. 9-216984 and WO 00/01748.
The acrylic polymer and acrylsol described in these documents satisfy fundamental performances required for plastisol, that is, viscosity stability during storage and plasticizer-retaining property of molded articles or cured films after being heated and cured. However, they still have a problem in that their viscosity is higher than that of vinyl chloride sol. Thus, there is further increasing demand for techniques of decreasing viscosity.
As a method for decreasing the viscosity of plastisol, a method of increasing the amount of a plasticizer is generally considered. However, a cured plastisol product containing a higher amount of a plasticizer may cause more bleeding out of the plasticizer, and the mechanical strength may decline.
Further, a diluent used for decreasing the viscosity of plastisol is unfavorable from the viewpoint that organic matters vaporize during molding.
Hence, a low viscosity acrylsol containing hydroxy fatty acid/polyhydric alcohol ester is proposed in Japanese Patent Laid-Open No. 2001-187834.
The hydroxy fatty acid/polyhydric alcohol ester described in Japanese Patent Laid-Open No. 2001-187834 has a low effect of decreasing viscosity depending upon a plasticizer selected, and higher viscosity decreasing effect is required particularly for di-2-ethylhexyl phthalate or diisononyl phthalate that are cheap and used widely. In addition, coloring derived from hydroxy fatty acid/polyhydric alcohol ester is sometimes observed in obtained film or molded product.